Daily Broadcaster

Shanghai, China- October 29, 2026

When buying PP sheet rolls for thermoformed packaging, “anti-block” is sometimes treated as a simple surface-treatment option. In practice, it can affect how the sheet unwinds, feeds, separates, and behaves during thermoforming.

One of the key properties behind this behavior is the coefficient of friction (COF).

A good anti-block PP sheet is not simply a sheet that “does not stick.” The surface has to provide the right balance between blocking resistance and controlled friction. If the surface is too slippery, feeding and stacking behavior can change. If it is too tacky, sheets can stick together or become difficult to handle.

For thermoforming buyers, the important question is therefore not just whether a PP sheet is anti-block, but whether its surface friction is suitable for the actual production process.

What Is Anti-Block PP Sheet?

PP has relatively good surface properties, but two polymer surfaces can still develop unwanted adhesion when they are pressed together, especially under pressure, heat, or long storage periods.

This phenomenon is generally called blocking.

In sheet and roll production, blocking can create practical problems:

• Adjacent layers of a roll may become difficult to separate.

• Sheets can stick during stacking and handling.

• Feeding into a thermoforming line may become less consistent.

• Automatic sheet separation can become more difficult.

• Surface appearance may be affected if excessive force is required to separate layers.

Anti-block technology is used to reduce this tendency.

Depending on the material design, anti-block performance can come from additives or surface structures that create microscopic separation between contacting surfaces. The objective is not necessarily to make the PP surface extremely smooth or extremely slippery. It is to prevent unwanted surface-to-surface adhesion while maintaining useful handling characteristics.

This distinction is important when comparing suppliers.

Anti-Block and COF Are Related, But They Are Not the Same Thing

A common purchasing mistake is to assume:

Lower COF = better anti-block performance.

That is not necessarily true.

Coefficient of friction describes the resistance between two surfaces when they move against each other. In practical thermoforming operations, buyers may care about both static friction and dynamic friction.

• Static COF relates to the force required to start movement.

• Dynamic COF relates to the friction during continued movement.

Anti-block performance, on the other hand, is mainly concerned with preventing two surfaces from adhering or becoming difficult to separate.

The two properties can influence each other, but they should not be treated as interchangeable specifications.

For example, a sheet may separate easily from another sheet but still have a relatively high COF during machine feeding. Conversely, a very low-friction surface may feed differently from the material used in an existing production line.

This is why I would not recommend selecting an anti-block PP roll based on a single COF number.

Why Does COF Matter on a Thermoforming Line?

For a thermoforming sheet manufacturer, the most important point is not the laboratory number itself. It is what happens when the roll enters the customer’s production line.

PP rollstock may pass through multiple stages before the final forming operation:

Unwinding → feeding → heating → forming → trimming → stacking or handling

At these stages, the surface characteristics of the sheet can influence material movement.

1. Roll unwinding

A roll that has excessive surface interaction between layers may require more force to unwind or separate.

This can become more noticeable with long storage periods, high winding pressure, elevated temperatures, or unsuitable storage conditions.

2. Automatic feeding

Thermoforming lines need predictable sheet movement.

If the surface friction changes significantly from one batch to another, the feeding behavior may also change. In high-speed production, even relatively small differences can become noticeable when the sheet is indexed repeatedly.

3. Sheet separation

After heating and forming, handling systems may need to separate individual parts or sheets. Surface friction can influence how easily materials move against guides, belts, or other surfaces.

4. Stacking and downstream handling

For certain applications, the finished thermoformed parts need to stack or separate in a controlled way. The required surface behavior depends on the design of the finished part and the downstream equipment.

This is why “more slippery” is not automatically the correct target.

What Does Anti-Block Actually Change on the PP Surface?

Anti-block additives or surface structures generally work by reducing the effective contact area between two surfaces.

Instead of two relatively smooth polymer surfaces making broad contact, microscopic irregularities create small separation points.

This can reduce the tendency of the surfaces to stick together.

However, changing the surface also has potential trade-offs.

Depending on the formulation and concentration, anti-block treatment can influence:

• Surface friction

• Transparency or haze

• Surface appearance

• Printing performance

• Adhesion

• Sealing behavior

• Thermoforming surface appearance

• Contact with downstream equipment

This is one reason why a sheet supplier should not optimize anti-block performance independently from the rest of the PP formulation.

The correct surface is the one that works with the customer’s complete process.

Anti-Block PP Does Not Mean “The Lowest Possible Friction”

This is probably the most useful point for buyers.

Imagine two PP sheets:

Sheet A: very low COFSheet B: moderate and controlled COF

It may be tempting to assume Sheet A is superior. But if the thermoforming line was designed around Sheet B’s feeding characteristics, changing to an extremely slippery material could create unexpected behavior.

The same applies to stacking.

A certain amount of friction can sometimes be useful for keeping materials in a controlled position. The ideal value depends on the equipment, sheet thickness, forming process, and downstream handling.

Therefore, I recommend discussing COF as a process parameter, not as an isolated performance ranking.

What Should Buyers Ask a PP Sheet Supplier?

If anti-block performance is important, a useful inquiry should include more than:

“Please quote anti-block PP sheet.”

At minimum, provide the following information:

Item	Why It Matters
PP grade	Different formulations behave differently
Sheet thickness	Influences stiffness and feeding
Roll width	Must match the thermoforming line
Application	Helps determine surface requirements
Forming process	Provides context for feeding and heating
Printing requirement	Anti-block formulation may affect surface compatibility
Sealing requirement	Important for applications using heat sealing downstream
Existing material	Useful for matching current production behavior
COF requirement	Should be discussed with the test method
Anti-block requirement	Clarifies the actual problem to solve

For reference, PULIXIN’s current product information lists normal PP sheet rolls at approximately 0.3–2.0 mm thickness and 300–900 mm width, with exact thickness depending on the grade.

However, anti-block PP should be specified according to the actual project rather than assumed to have one universal specification.

COF Test Results Are Meaningless Without the Test Conditions

This is another point that is often missed in international purchasing.

A COF value should always be considered together with the test method and conditions.

Important variables can include:

• Counter-surface material

• Test speed

• Normal load

• Temperature

• Humidity

• Film or sheet orientation

• Surface condition

• Static versus dynamic measurement

Therefore, comparing “COF = 0.25” from one supplier with “COF = 0.30” from another supplier may not be meaningful if the test conditions are different.

For a serious production project, I would rather have a clearly defined test method and a repeatable range than a single attractive number without test context.

Anti-Block PP and Thermoforming: What Should Be Validated?

Before placing a large production order, buyers should test the actual PP roll on the intended thermoforming equipment.

The validation should include more than simply checking whether two sheets separate.

Look at:

Roll handling

Does the roll unwind smoothly? Is there abnormal telescoping, sticking, or excessive tension?

Feeding

Does the sheet move consistently through the feeding system?

Heating

Does the anti-block surface create any unexpected surface appearance after heating?

Forming

Does the material maintain the required forming behavior and surface quality?

Trimming and stacking

Can the formed parts move through the downstream process without excessive sticking or uncontrolled sliding?

Printing or sealing

If the finished application requires printing, bonding, or sealing, confirm compatibility with the actual production process.

The purpose of a material trial is not simply to prove that the PP is “good.” It is to determine whether the sheet behaves predictably on the customer’s equipment.

Common Buying Mistakes With Anti-Block PP SheetMistake 1: Choosing only by the lowest COF

A lower number does not automatically mean better production performance.

Mistake 2: Treating anti-block and slip as identical

They are related surface properties, but they solve different problems.

Mistake 3: Comparing COF numbers without test conditions

A COF value without its test method is incomplete information.

Mistake 4: Testing only the raw sheet

The real application involves heating, forming, trimming and handling. The material should be evaluated under representative processing conditions.

Mistake 5: Ignoring other surface requirements

If the sheet will later be printed, sealed, bonded, or laminated, anti-block performance should be considered together with those requirements.

A Practical Way to Specify Anti-Block PP Roll

For most purchasing projects, I recommend starting with the production problem rather than asking for a predefined additive package.

A useful specification might look like this:

PP material → target thickness → roll width → thermoforming application → anti-block requirement → COF target/range if required → test method → printing/sealing requirements → trial validation

This gives the sheet manufacturer enough information to recommend a suitable material structure instead of simply matching a keyword such as “anti-block.”

For example, if your current PP roll sticks during unwinding, the solution may involve surface design, winding conditions, storage conditions, or a combination of factors. If the problem is unstable feeding, COF and equipment interaction become more important.

Those are different problems, even though both may initially be described as “the PP sheet is sticking.”

Final Takeaway

Anti-block PP sheet is not simply PP with a lower tendency to stick. For thermoforming production, the more useful way to evaluate it is to look at blocking behavior, coefficient of friction, processing conditions, and downstream handling together.

COF is an important surface property, but it should not be used as a single indicator of material quality. The right target depends on the thermoforming line, sheet thickness, application, and downstream requirements.

For buyers sourcing PP sheet rolls, the best approach is to define the production problem first, then confirm the anti-block design, COF test conditions, sheet specifications, and actual machine performance with the supplier.

That usually leads to a more reliable material selection than simply asking for the “lowest-friction PP sheet.”

Frequently Asked QuestionsIs anti-block PP the same as low-friction PP?

No. Anti-block PP is designed primarily to reduce unwanted surface adhesion. COF measures resistance to movement between surfaces. The properties are related but not identical.

Does a lower COF always mean better PP sheet?

No. An excessively low COF may change feeding, stacking, or downstream handling behavior. The appropriate friction level depends on the production equipment and application.

Can anti-block PP affect transparency?

It can. Depending on the anti-block technology and formulation, changes to the surface can influence haze or appearance. If transparency is important, it should be included in the material specification.

Should COF be tested before ordering PP rolls?

Yes, especially when surface friction is critical to feeding or downstream handling. Make sure the test method and conditions are defined so that results can be compared meaningfully.

What information should I provide when requesting anti-block PP sheet rolls?

Provide the material, thickness, roll width, application, thermoforming process, current material if available, anti-block requirement, and any printing, sealing, or surface-friction requirements. If you have an existing COF target, provide the test method as well.

About us

Pulixin Packaging Materials (Shanghai) Co., Ltd. was established in 2009 in Shanghai. Its registered capital is RMB 20.8 million and area is more than 20,000 square meters. We are a manufacturer and seller of PP, PS, PET sheets etc . Our company owns 12 PET/PP/PS co-extruded production lines which import from Europe , and 2 coating production lines. Our production volume has been more than 40,000 metric tons per year. Our company products are mainly used in packaging for electronics, food, toys, cosmetics, medical, toys, printing and other industries.

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